Atomically precise Au₂₄(SR)₂₀ nanoclusters with multiemission

Area of Science:

• Materials Science
• Nanotechnology
• Photochemistry

Background:

• Atomically precise metal nanoclusters (NCs) exhibit tunable photophysics, but their photoluminescence (PL) mechanisms are not fully understood.
• Understanding these mechanisms is crucial for developing advanced nanomaterials with tailored optical properties.

Purpose of the Study:

• To elucidate the unified triple-emission mechanism in a series of Au24(SR)20 nanoclusters with varying R groups.
• To investigate the role of R groups in modulating excited-state dynamics and photoluminescence characteristics.

Main Methods:

• Utilized cryogenic photoluminescence (PL), femtosecond transient absorption, and time-resolved electron paramagnetic resonance spectroscopy.
• Studied a correlated series of Au24(SR)20 nanoclusters with identical cores but different R groups.

Main Results:

• Provided the first direct experimental evidence for a short-lived excited triplet state (T1) with a ~350 ns lifetime at room temperature.
• Resolved the exciton relaxation cascade from singlet states (S1) to the T1 state, contributing to multiemission across visible to near-infrared wavelengths.
• Demonstrated that ligand R group symmetry, specifically in 3,5-dimethylbenzylthiolate, enhances rigidity, inhibiting structural distortion and slowing intersystem crossing, leading to improved fluorescence.

Conclusions:

• Established a unified triple-emission mechanism in Au24(SR)20 nanoclusters governed by R group modulation of excited-state dynamics.
• Proposed a paradigm for designing efficient, multiemissive nanoclusters by controlling excited-state dynamics and spin character through ligand design.